Bactericidal Activity of Different Forms of Lactoferrin

Abstract

Mucosal surfaces provide the portal of entry for most pathogenic microorganisms. In protection the mammalian host has concentrated a number of defense factors in the exocrine secretions that bathe mucosal surfaces. Understanding how these factors operate to prevent pathologic consequences of microbial challenge and what mechanisms a pathogen uses to evade this host defense is essential to the development of interventive approaches. Lactoferrin (LF) and secretory IgA (slgA) are both secreted in significant quantities at most mucosal surfaces and in milk. Both of these factors are reported to have bacteriostatic activity (1–8) and interact with each other and other defense factors (including lysozyme, complement, and lactoperoxidase) to modify their effectiveness (9, 10). In addition purified iron-free LF has been shown to have microbicidal activity against a variety of bacteria and yeast via mechanisms that are not reversed by the addition of free iron (11–16). A factor present in many commercial LF-enriched preparations, which co-purifies with slgA, has been reported to result in syner-gistic bactericidal activity and these impure LF preparations are able to kill bacterial strains that are resistant to purified LF (17).